An on-behalf-of boundary limits an agent to the privileges of the human or service identity it is acting for. It prevents free-floating privilege growth by ensuring the agent cannot exceed the authority of the principal whose intent initiated the task.
Expanded Definition
An on-behalf-of boundary is a governance and execution constraint that keeps an agent or automated workflow inside the authority of the principal it represents. In NHI terms, that principal may be a human user, a service account, or another approved workload identity. The boundary matters because agentic systems can chain actions, call tools, and request tokens in ways that quietly expand privilege unless the delegation model is explicit.
Definitions vary across vendors, but the practical pattern is consistent: the agent may act, yet it must not invent new authority, bypass approval, or retain credentials beyond the intended task. This is closely related to delegated access and least privilege, and it aligns with the intent of NIST Cybersecurity Framework 2.0 around access control and continuous governance. NHI Management Group treats the boundary as an anti-exposure control for agentic execution, not as a generic application permission rule.
The most common misapplication is allowing the agent to exchange a user’s intent for durable operational privilege, which occurs when token scope, session lifetime, or downstream tool access are not constrained to the original principal.
Examples and Use Cases
Implementing an on-behalf-of boundary rigorously often introduces coordination overhead, requiring teams to weigh automation speed against stronger approval, scope, and token-lifetime controls.
- A helpdesk copilot creates tickets only within the permissions of the requesting technician, and cannot read unrelated records even if it can reach the same backend API.
- An ops agent rotates a secret on behalf of a service owner, but the delegation token expires after the change window and cannot be reused for follow-on actions.
- A finance workflow approves a vendor payment only when the agent presents evidence tied to the initiating user, rather than escalating to broader payment privileges.
- A CI/CD agent deploys infrastructure with the build service identity, but cannot assume a separate production admin role unless a human-approved boundary allows it.
- For governance references on delegated NHI control patterns, the Ultimate Guide to NHIs is a useful baseline, especially when paired with identity assurance concepts from NIST Cybersecurity Framework 2.0.
Why It Matters in NHI Security
On-behalf-of boundaries reduce the blast radius of compromised agents, mis-scoped service accounts, and over-permissioned toolchains. Without them, an agent can become a privilege multiplier: one intended task is enough to unlock unrelated secrets, administrative endpoints, or persistent access paths. That is especially dangerous in environments where NHIs already outnumber human identities by 25x to 50x, and where 97% of NHIs carry excessive privileges, according to NHI Management Group research in the Ultimate Guide to NHIs.
This boundary also supports zero trust by forcing every delegated action to be evaluated against the current principal, context, and task intent. It complements policy and telemetry guidance in NIST Cybersecurity Framework 2.0 and reduces the chance that a temporary automation becomes a standing backdoor. Organisations typically encounter the damage only after an agent has already overreached or a token has been replayed, at which point the on-behalf-of boundary becomes operationally unavoidable to address.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
OWASP Non-Human Identity Top 10 and OWASP Agentic AI Top 10 address the attack and risk surface, while NIST CSF 2.0, NIST Zero Trust (SP 800-207) and NIST SP 800-63 set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| OWASP Non-Human Identity Top 10 | NHI-04 | Delegated agent authority must not exceed the initiating principal's scope. |
| OWASP Agentic AI Top 10 | A-03 | Agent tool use and delegation boundaries are central to preventing runaway authority. |
| NIST CSF 2.0 | PR.AC-4 | Access permissions must be managed according to least privilege and context. |
| NIST Zero Trust (SP 800-207) | SA-4 | Zero trust requires continuous evaluation of identity, device, and session trust. |
| NIST SP 800-63 | AAL2 | Assurance levels inform how strongly a delegated identity must be bound to the actor. |
Constrain agent tokens and tool access to the principal's exact task and session boundary.
Related resources from NHI Mgmt Group
- Why has identity replaced the network perimeter as the primary security boundary?
- When should organisations treat package registries as a security boundary?
- What breaks when container authorization fails open at the API boundary?
- How should security teams authorize API requests made by applications on behalf of users?
